Testosterone Cypionate is the longest-estered testosterone
available today. It has a half-life in the body of 15 to 16 days
and is found as injectable oil. Because it reacts in the body for
so long, it can cause more water retention than other steroids and
is best used as bulking compound in a stack.

As with all testosterone injectables, one can expect a considerable
gain in muscle mass and strength during a cycle. Since testosterone
readliy converts to estrogen, the mass gained from this drug is
likely to be accompanied by quite a bit of water retention. The
resulting loss of definition of course makes cypionate a very poor
choice for dieting or cutting phases. The excess level of estrogen
brought about by this drug can also cause one to develop
gynecomastia rather quickly. Should one notice an uncomfortable
soreness, swelling or lump under the nipple, an ancillary drug like
Nolvadex should be added immediately. This will minimize the effect
of estrogen greatly, making the steroid much more tolerable to use.
The powerful anti-aromatases Arimidex, Femara, or Aromasin are yet
a better choice. Those who have a known sensitivity to estrogen may
find it more beneficial to use ancillary drugs like Nolvadex and
Proviron from the onset of the cycle, in order to prevent estrogen
related side effects before they become apparent.